Preheat the oven to 180°C top and bottom heat. Grease a springform pan (Ø 28 cm diameter).
Using a hand mixer, whisk butter until creamy. Add salt, sugar and egg and mix thoroughly.
Mix flour and baking powder and add alternately with the milk to the butter-sugar mixture until the dough is torn. Pour the dough into the greased springform pan and spread evenly with a damp spoon.
For the crumble, mix flour, sugar, almonds and vanilla sugar thoroughly. Add the soft butter in pieces and knead with your hands until coarsely crumbled crumbs form. If the crumble is too soft, add a little more flour. Refine with cinnamon to taste.
Place the blueberries on the dough. Spread the crumble evenly over the fruit with your hands. Bake the cake for approx. 50 - 55 minutes
The crumble cake is ready when you prick it in the middle with a wooden stick and nothing sticks.
Here you can find some of the ingredients for the recipe